Speed ratio measuring system

ABSTRACT

A ratio counter provides a measure of the speed ratio of a cooperative pair of work rolls on a reversing roughing mill by counting a preset number of pulses generated by a first pulse tachometer attached to the motor drive shaft of one of the rolls and the number of pulses generated during the same period of time by a second pulse tachometer attached to the motor drive shaft of the other work roll. The output of the ratio counter is applied to the input of a digital printer. The ratio counter supplies the printer with a print command after each ratio measurement, but the printer remains inert until activated by an alarm system. The alarm system functions to activate the printer only when the roll speed ratio falls outside a predetermined range. The alarm system includes a first counter means for counting up to the same preset number of pulses from the first tachometer as does the ratio counter and a second counter means for counting a preselected number of pulses from the second pulse tachometer which number is less than that preset number of pulses. The system also includes a third counter means for counting the number of pulses generated by the second pulse tachometer between the time the second counter reaches said preselected number of pulses and the first counter reaches said preset number of pulses. Means are provided for developing in response to the count present in the third counter at the time the first counter reaches said preset number of pulses an output constituting a representative measure of the ratio of the number of pulses generated by the first pulse tachometer to the number of pulses generated by the second pulse tachometer during the period the first counter is counting up to the preset number; and when that output is outside a predetermined range, the printer is activated.

Sylvester et a1.

SPEED RATIO MEASURING SYSTEM Robert A. Sylvester, Coraopolis; Ronald W.Young, Beaver, both of Pa.

[72] inventors:

[73] Assignee: Jones & Laughlin Steel Corporation, Pittsburgh, Pa.

Mar.'26, 1969 [52] US. Cl. ..235/92 DN, 235/92 R, 235/92 PE, 235/92 CC,235/15 1.32 Int. Cl. ..B21c 51/00 Field otSearch ..235/92, 151.13,151.32, 151.38

[56] References Cited UNITED STATES PATENTS Primary Examiner-Maynard R.Wilbur Assistant Examiner-Robert F. Gnuse Attorney-T. A. Zalenski and G.R. Harris [57] ABSTRACT A ratio counter provides a measure of the speedratio of a cooperative pair of worlt rolls on a reversing roughing millby counting a preset number of pulses generated by a first pulsetachometer attached to the motor drive shaft of one of the rolls and thenumber of pulses generated during the same period of time by a secondpulse tachometer attached to the motor drive shaft of the other workroll. The output of the ratio counter is applied to the input of adigital printer. The ratio counter supplies the printer with a printcommand after each ratio measurement, but the printer remains inertuntil ac- V tivated by an alarm system. The alarm system functions toactivate the printer only when the roll speed ratio falls outside apredetermined range. The alarm system includes a first counter means forcounting up to the same preset number of pulses from the firsttachometer as does the ratio counter and a second counter means forcounting a preselected number of pulses from the second pulse tachometerwhich number is less than that preset number of pulses. The system alsoincludes a third counter means for counting the number of pulsesgenerated by the second pulse tachometer between the time the secondcounter reaches said preselected number of pulses and the first counterreaches said preset number of pulses. Means are provided for developingin response to the count present in the third counter at the time thefirst counter reaches said preset number of pulses an outputconstituting a representative measure of the ratio of the number ofpulses generated by the first pulse tachometer to the number of pulsesgenerated by the second pulse tachometer during the period the firstcounter is counting up to the preset number; and when that output isoutside a predetermined range, the printer is activated.

3 Claims, 2 Drawing Figures I: l5 ll 22 RATIO DIGITAL couu en T nnmrsn2o 16 14' ENABLE DIGITAL TIME CLOCK 49 mssmwvc: 55 Puss N0. 42 W COUNTER5i RESET PERCENT PERCENT f msmrcn ALARM 25 43 READOUT SELECTOR Y rm: useL. l

couursn MILL LOADED nzssr ENABLE INPUT 1 4 RESET PERCENT MEMORY BINARYTO STOP nzncsm' COMMAND ozconzn nsszr ENABLE E L RESET u PERCENT EPERCENT counrsn GATE :0 couursn 2s DISABLE 23 x 27 29 RCENT MULYIPLIER31 snscron PATENTEU IIII25I9I2 $631998 SHEET l 6?- II I I3 22 mac /yRATIo 553% Q J L I6 I4 ENABLE I DIGITAL T CLOCK 47 L 48 vARIABLE PRINT49 TIMER so PASS ADVANCE PASS PASS No. 42 46 INPUT couNTER f I 5| IIREsET PERcENT PERCENT FLAST PASS MISMATCH ALARM INPuT 4 REAoouTsELEcToR Y TIME BAsE DELAY couNTER CIRCUIT Q LOADED RESET ENABLE INPUT 74.4

sTART RESET M PERCENT I COMMAND MEMORY I BINARY To STOP PERCENTIVCOMMAND DECODER /37 RESET, ENABLE VRESET NA x TAcI-I PERCENT E PERCENTcouNTER GATE 3o couNTER J DISABLE H L2? 29 PERcENT MULTIPLIER sIsELEcToR INVENTORS ROBERT A. SYLVESTER RONALD W. YOUNG ATTORNEY SPEEDRATIO MEASURING SYSTEM This invention relates generally to a system formeasuring the speed ratio of two moving bodies and recording ratio measurements which exceed or lag a preselected range. More particularly,the invention relates to a digital system for measuring accurately thespeed ratio of the working rolls in a typical rolling mill.

It has been discovered that surface defects in steel strip or sheet canbe originally formed during the rolling of the steel slab into abreakdown bar. Specifically, it has been found that a speed mismatchbetween the top and bottom work rolls in a reversing roughing mill canresult in the formation of embedded oxides in the breakdown bar. Theembedded oxides are retained in the steel surface as it is furtherprocessed to strip, where they show up as defects in the strip surface.These defects are particularly evident in tin plate where they appear asminute slivers and are associated with accelerated corrosion of cans inlocalized ares, mechanical failures in can lids, blisters in lacquer,poor surface appearance and poor solderability.

Should a steel slab be roughed with fire-cracked rolls, hot steel isextruded into the fire cracks during rolling, forming small protrustionson the slab surface. If the roughing mill work rolls are rotating atdifferent speeds, the protrusions are abraded as they disengage from therolls, capturing a small amount of scale. On subsequent passes or at thefinishing stands, the occluded scale is rolled into the surface of theslab, forming an embedded oxide deposit. The problem is alleviated bysynchronizing the speeds of the work rolls.

Accordingly, an object of the present invention is to provide a systemfor noting any disparity in the rotative speeds of a cooperative pair ofwork rolls on a reversing roughing mill. Another object of the invention'is to provide such a system which measures the speed ratio ofthe work rolls. Still another object of the invention is to provide sucha speed ratio measuring system where the speed ratio is recorded onlywhen it exceeds or lags a preselected speed ratio range. Yet anotherobject of the invention is to provide a system for measuring the speedratio of two moving bodies and for recording ratio measurements fallingoutside a preselected range.

Briefly, the invention includes a ratio counter which counts a presetnumber of pulses from a first pulse tachometer attached to the motordrive shaft of one of a pair of roughing mill work rolls and displaysthe number of pulses counted during the same period from a second pulsetachometer attached to the motor drive shaft of the other work roll. Theoutput of the ratio counter is applied to the input of a digitalprinter. The counter supplies the printer with a print command aftereach ratio measurement but the printer remains inert until activated bythe alarm sectionof the system.

When the roll speed ratio falls outside a predetermined range, the alarmsection activates the printer and it prints out, for a desired timeperiod, the speed ratio measurement, the time and the pass number. Thesystem thus provides automatic 24 hour surveillance of mill operationand alerts mill personnel when a severe speed mismatch of the work rollsexists. This gives the production personnel an opportunity to takeimmediate corrective measures.

The invention will now be described in greater detail with reference tothe accompanying drawing in which:

FIG. 1 isa detailed block diagram of the system of the invention; and

FIG. 2 is two charts setting forth the relationship between specificsystem variables.

Referring to FIG. I, a steel slab is illustrated as passing through atop work roll ll and bottom work roll 12 of a typical reversing roughingmill. A high resolution pulse tachometer 13 is connected to the rollmotor drive shaft 15 driving roll 11 and a similar tachometer 14 isconnected to the roll motor drive shaft 16 driving roll 12. Thetachometers, of course, generate electrical pulses in response to and ata rate dependent on the speed of the drive shafts and work rolls. Thetachometers are connected to the drive shafts through suitable step-upgears in increase the number of pulses generated per shaft revolution,thereby obtaining a more significant measure of the rotative speeds ofthe drive shafts and their depending work rolls.

The outputs of tachometer l3, referred to herein as X pul ses, andtachometer l4, referred to herein as Y pulses, are fed to a commercialratio counter 20.which develops outputs each of which constitutes ameasure of the speed ratio of the work rolls during the generation of -adiscrete number of pulses, defining a counting period, by a tachometer14. Thus, ratio counter 20 counts 1,000 pulses from tachometer l4 anddisplays the number of pulses counted from tachometer l3 during thatcounting period. The output of the ratio counter, which represents 1,000X/Y and the speed ratio of the work rolls, is applied to the input of adigital printer 21 for recording of the outputs developed by..the ratiocounter. The ratio counter supplies the printer with a print or recordcommand via line 22 after each ratio measurement, that is, after eachcount of 1,000 Y pulses by the ratio counter or at the end of eachcounting period. The alarm system controls the operation of the printerto render it operative to record the outputs developed by the ratiocounter when the speed ratio falls outside a selected range, as will nowbe described.

Y pulses from tachometer 14 are also fed to time base counter 25, whileX pulses from tachometer 13 are also fed to tach counter 26 and percentcounter 27. Each of these counters comprise ordinary binary codeddecimal counters. Percent gate 28 is operatively connected to tachcounter 26 to develop an output upon tach counter 26 counting aprescribed number of X pulses. The prescribed number of pulses, for thesystem described, may be 920 or 960 and is controlled by means ofpercent multiplier selector 29. The selector 29 comprises, in effect, aswitch which in a first position permits enabling of gate 28 to developan output when tach counter 26 develops an output corresponding to 960counted pulses and in a second position permits enabling of gate 28 todevelop an output when tach counter 26 develops an output correspondingto 920 counted pulses. The output developed by gate 28 enables percentcounter 27 via line 30 and disables tach counter 26 via line 31.

Time base counter 25 counts 1,000 Y pulses in the same period of timeratio counter 20 counts 1,000 Y pulses. Tach counter 26 simultaneouslycounts X pulses until it has counted 920 or 960 pulses, depending on thepositioning of selector 29. Thereafter, X pulses are counted in percentcounter 27 until time base counter 25 has counted 1,000 Y pulses, i.e.,until the end of the counting period. At that time the carryout ofcounter 25 is used to develop, through the line 35, a stop command 36which by means of line 27 resets counters 26 and 27 and disables thelatter counter. It will be understood that the number of pulses percentcounter 27 counts up until time base counter 25 counts 1,000 Y pulses isa measure of the speed ratio of the working rolls [1 and 12.

Decoder 40, decodes the .binary number accumulated in percent counter 27to indicate the percent speed mismatch of the top roll with respect tothe bottom roll. The output of the decoder is applied to percent memory41, which, each time counter 25 counts 1,000 Y pulses, develops anoutput measurably responsive to the speed ratio. Memory 41 comprises aseries of six gates. When a gate is enabled by the output of decoder 40,a flip-flop associated with the gate is set and, in turn, as associatedrelay is set. The decoder output is, of course, a function of the binarynumber accumulated in counter 27 and accordingly will activate the oneof the six gates of memory 41 which corresponds to that number. This maybe better seen with reference to FIG. 2. The left-hand chart of FIGJ2corresponds to the condition when selector 29 is in its first positionand tach counter 26 is disabled after registering 960 pulses. Theleft-hand column of the chart lists a series of X pulse values which maybe counted while time base counter 25 counts 1,000 Y pulses. The middlecolumn lists the readout values from memory 41 which correspond to thelisted X pulse values. The right column lists the verbal meaning of thememory readouts.

it will be understood that when the total X pulse count is 1,040, theaccumulated count in counter 27 is 80. Decoder 40 decodes binary 80 toan output which can activate only one of the gates in memory 41 settingan associated flip-flop and relay to provide a memory readout in percentmismatch readout 42 at the 1 3% position. The decoder output developedby binary numbers 71 through 80 activates this same gate to provide areadout in the +3% position, which means that there is a speed mismatchbetween the top and bottom rolls of more than +3%.

For the decoder output developed by binary numbers 61 through 70accumulated in counter 27, a second gate is activated setting anassociated flip-flop and relay to provide a memory readout in percentmismatch readout 42 at the +2% position. This readout means that thespeed mismatch is greater than +2% but less than or equal to +3%. In asimilar manner, as indicated on the chart, different ranges of binarynumbers accumulated in counter 27 are uniquely related to specificmemory readouts which have specific verbal meanings. in the embodimentof the invention described herein, six such bands and associatedreadouts are provided. There is, of course, a seventh condition and thatis the condition when there is no memory readout. This occurs, as shownon the chart, when he speed mismatch is greater or equal to l%, but lessor equal to+l%.

The right-hand chart of FIG. 2 gives the relationship between total Xpulse count, memory readout and verbal meaning when the percentmultiplier 29 is in the second position, that is, tachometer 26 isdisabled after counting 920 X pulses. When selector 29 is placed in itssecond position, a divide-by-two counter associated with counter 27 isautomatically activated. Consequently, when counter 26 reaches 920 andcounter 27 enabled, only one-half of the X pulses delivered to counter27 are registered therein. As a result, under these conditions, a totalX pulse count of between 1,061 and 1,080 results in an accumulation ofbetween 71 and 80 in counter 27 and, as shown on the chart, produces amemory readout in the +3% position which, in this case, corresponds to aspeed mismatch of +6%. Thus, a particular accumulated count in counter27 will result in the same memory readout whether selector 29 is in afirst or second position, but the verbal meaning is difi'erent as shownon the charts of FIG. 2.

The carryout of time base counter 25 is also applied to a 200millisecond delay circuit 43 which generates a start command, enablingcounters 25 and 26 to start counting and resetting memory 41. At thebeginning of the rolling of the slab a mill loaded signal is deliveredthrough line 45 to generate the start command.

Percent alarm selector switch 46 is operatively connected to memory 41and variable print timer 47. Upon receiving an input from memory 41,percent alarm selector 46 activates timer 47 to enable printer 21. Theprinter will continue to record the speed ratios supplied by ratiocounter 20 for an interval the duration of which is dependent on thetimer setting. The percent alarm selector 46 is wired to memory 41 insuch a manner that production personnel can select the roll speedmismatch which alarms the system. For example, if the 2% position of thepercent alann switch is selected, all mismatches greater or equal to +2%and less or equal to 2% will activate the printer.

A digital clock 48 and pass counter 49 are also provided. Theirrespective outputs are applied to the printer to provide a parallelrecord of the pass number the slab 10 is undergoing and the time atwhich the excessive speed mismatch occurs.

The pass counter records the pass numbers from a pass advance" inputdelivered through line 50 and is reset by means of a last pass" inputthrough line 51. The pass advance and last pass inputs, as well as themill loaded" input are developed from contact closures of relays in themills control system. These relays perform control functions during thebreakdown of the slab in the mill. A contact from each of these relayscontrols an interface relay in the alarm system. The action of theinterface relays are in turn utilized to develop a control pulsecompatible with the solid state circuitry used in the alarm system.

We clarm:

1. Apparatus for measuring the speed ratio of first and second movingbodies comprising first and second means for generating electricalpulses in response to and at a rate dependent on the speed of said firstand second moving bodies respectively, ratio measuring means forreceiving the pulses developed by said first and second means to developelectrical outputs each of which constitutes a measure of the speedratio of the two bodies during the generation of a discrete number ofpulses, defining a counting period, by one of said pulse generatingmeans, said ratio measuring means including means for issuing a recordcommand to a recording means after each speed ratio measurement, andmeans controlling the operation of the recording means to render itoperative to record the outputs developed by the ratio measuring meanswhen the speed ratio falls outside a selected range, said controllingmeans comprising memory means for developing at the end of each countingperiod an output measurably responsive to the speed ratio during thecounting period, selector means for delivering the output of the memorymeans to a means for activating the recording means when that outputrepresents a speed ratio falling outside said selected range, means forcounting during each counting period a portion of the pulses generatedby one of said first and second means for generating pulses, saidportion of the pulses being a measure of the speed ratio during thatcounting period, and means for applying to said memory means, in theform of electrical inputs, the count in said counting means.

2. Apparatus for measuring the ratio of electrical pulses generated bytwo pulse-generating means comprising, a first counter means forcounting a first preselected number of electrical pulses from a firstelectrical pulse-generating means, a second counter means for counting asecond preselected number of electrical pulses less than said firstpreselected number from a second electrical pulse-generating means, athird counter means for counting the number of electrical pulsesgenerated by said second generating means between the second countingmeans reaching said second preselected number and the first countingmeans reaching said first preselected number, means for developing inresponse to the count in said third counter means an output constitutinga representative measure of the ratio of the number of pulses generatedin said first generating means to the number of pulses generated in saidsecond generating means during the period the first counter means iscounting up to said first preselected number.

3. The apparatus of claim 2 wherein the carryout of said first countermeans is adapted upon reaching the first preselected number to develop astop command to reset the first, second and third counter means and tobe applied to a delay circuit for generating a start command to enablethe first and second counter means and reset the memory means.

r: r: e a a

1. Apparatus for measuring the speed ratio of first and second movingbodies comprising first and second means for generating electricalpulses in response to and at a rate dependent on the speed of said firstand second moving bodies respectively, ratio measuring means forreceiving the pulses developed by said first and second means to developelectrical outputs each of which constitutes a measure of the speedratio of the two bodies during the generation of a discrete number ofpulses, defining a counting period, by one of said pulse generatingmeans, said ratio measuring means including means for issuing a recordcommand to a recording means after each speed ratio measurement, andmeans controlling the operation of the recording means to render itoperative to record the outputs developed by the ratio measuring meanswhen the speed ratio falls outside a selected range, said controllingmeans comprising memory means for developing at the end of each countingperiod an output measurably responsive to the speed ratio during thecounting period, selector means for delivering the output of the memorymeans to a means for activating the recording means when that outputrepresents a speed ratio falling outside said selected range, means forcounting during each counting period a portion of the pulses generatedby one of said first and second means for generating pulses, saidportion of the pulses being a measure of the speed ratio during thatcounting period, and means for applying to said memory means, in theform of electrical inputs, the count in said counting means. 2.Apparatus for measuring the ratio of electrical pulses generated by twopulse-generating means comprising, a first counter means for counting afirst preselected number of electrical pulses from a first electricalpulse-generating means, a second counter means for counting a secondpreselected number of electrical pulses less than said first preselectednumber from a second electrical pulse-generating means, a third countermeans for counting the number of electrical pulses generated by saidsecond generating means between the second counting means reaching saidsecond preselected number and the first counting means reaching saidfirst preselected number, means for developing in response to the countin said third counter means an output constituting a representativemeasure of the ratio of the number of pulses generated in said firstgenerating means to the number of pulses generated in said secondgenerating means during the period the first counter means is countingup to said first preselected number.
 3. The apparatus of claim 2 whereinthe carryout of said first counter means is adapted upon reaching thefirst preselected number to develop a stop command to reset the first,second and third counter means and to be applied to a delay circuit forgenerating a start command to enable the first and second counter meansand reset the memory means.